A printing blanket is known from DE 691 07 317 T2, which consists of several layers and, in an extreme case, has a total thickness of from 0.55 to 3.65 mm. The modulus of elasticity of the several layers of cellular rubber lies between 0.2 to 50 MPa, or between 0.1 to 25 MPa. Because of the special structure of the printing blanket, and because of the properties of the several layers, a printing blanket is obtained which, when indented, does not tend towards lateral shifting or protuberances.
DE 19 40 852 A1 discloses a printing blanket for offset printing, which blanket has a total thickness of almost 1.9 mm. A modulus of shearing, in the form of tension at 0.25 mm deformation in case of a thickness of the printing blanket, is stated to be approximately 4.6, 1.9 or 8.23 kg/cm2. The goal, in this case, is to achieve a quick recovery after an indentation, as well as to achieve a narrow thickness tolerance.
CH 426 903 discloses an offset printing blanket in which customary indentation depths of 0 to 0.1 mm exist. An increase of the indentation from 0.05 to 0.1 mm requires, or has, at a result, a change in the surface pressure of approximately 20.6 N/cm2. This means that, in this range of indentation depth and with surface pressures of up to approximately 40 N/cm2, there would be a linearized “spring characteristic” with a rise of approximately 412 N/cm2/mm.
WO 01/399 74 A2 discloses printing units with two cylinders, which two cylinders work together in the placed-together position. A forme cylinder has an opening, in the area of its surface, in the form of an axially extending groove for use in fastening one end of one or of several printing formes. A transfer cylinder, which acts together with the forme cylinder in a contact zone, has an elastic rubber blanket in the area of its surface.
For the transfer of ink and other fluids between two cylinders of a printing press, recourse is regularly had to the material combination of hard-soft, for example in an inking and/or dampening unit, as well as in the practice of an offset printing method between printing group cylinders. The surface pressure required for ink transfer between the two cylinders is achieved by making an indentation in a resilient, such as, for example, an elastomeric layer, which may be a soft elastomeric cover/dressing, rubber blanket, or metal printing blanket, sleeve, by a cooperating cylinder with a surface which is incompressible and which is also inelastic, to a large degree.
Essential criteria for the uniform transfer of the fluid between the cylinders are a contact pressure, which is preset within narrow margins, as well as the constancy of the contact pressure. If fluctuations occur in the spacing distance between the cooperating cylinders, for example because of cylinder out-of-roundness or because of vibrations induced by interferences with the roll-off of the cylinders, the contact force, or the surface pressure, changes, and thus the transfer behavior of the fluid also changes. At locations with interrupted or with reduced contact, for example at the location of the plate or rubber blanket tensioning groove, the surface pressure, for example, changes periodically. This periodic change in surface pressure results in a vibration excitation of the printing cylinders. In the field of printing technology, this change in surface pressure is expressed by changes in the ink intensity in the resulting printed image. If, for example, the contact pressure has been permanently changed through exterior conditions such as longer wave interference, the danger of too faint or of too color-intensive printed products exists until the time of correction. These products are typically considered as waste products. If the contact pressure is dynamically changed because of vibrations, such as shorter wave interference, this change in contact pressure is expressed by the formation of visible stripes in the printed product.